Merge #1137

1137: Adds support for multiple editor workspaces on initialization r=matklad a=jrvidal

OK, so this "simple hack" turned out to be way more contrived than I expected :joy:

### What works
This patch only handles multi-folder editor workspaces _on initialization_.
  * I've found that modifying the layout of a workspace in VSCode just reloads the extension, so this hack should be enough for now.
  * Not sure about how emacs-lsp behaves, but we fallback gracefully to the mono-folder workspace, so it should be fine.

### What doesn't work
* [x] `cargo watch` can only watch a single root folder with a `Cargo.toml`. I've left this part untouched but we could either warn that it's not supported or launch _multiple_ `cargo-watch` processes.
* [x] The `rust-analyzer/runnables` command is not functional, since we don't send the correct `cwd`.
* [x] Should we add some happy path test to `heavy_tests`?
* [ ] Going from a single `root` to multiple `roots` leaves us with a couple of `n * m` loops that smell a bit. The number of folders in the editor workspace is probably low though.

Co-authored-by: Roberto Vidal <[email protected]>

2 files changed, 14 insertions, 1 deletions

diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index 81cb506b7..71976071f 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -19,6 +19,7 @@ use crate::Result;
 pub struct CargoWorkspace {
     packages: Arena<Package, PackageData>,
     targets: Arena<Target, TargetData>,
+    pub(crate) workspace_root: PathBuf,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
@@ -165,7 +166,7 @@ impl CargoWorkspace {
             }
         }
 
-        Ok(CargoWorkspace { packages, targets })
+        Ok(CargoWorkspace { packages, targets, workspace_root: meta.workspace_root })
     }
 
     pub fn packages<'a>(&'a self) -> impl Iterator<Item = Package> + 'a {
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index 3bad4f8d3..63eb7041e 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -255,6 +255,18 @@ impl ProjectWorkspace {
         }
         crate_graph
     }
+
+    pub fn workspace_root_for(&self, path: &Path) -> Option<&Path> {
+        match self {
+            ProjectWorkspace::Cargo { cargo, .. } => {
+                Some(cargo.workspace_root.as_ref()).filter(|root| path.starts_with(root))
+            }
+            ProjectWorkspace::Json { project: JsonProject { roots, .. } } => roots
+                .iter()
+                .find(|root| path.starts_with(&root.path))
+                .map(|root| root.path.as_ref()),
+        }
+    }
 }
 
 fn find_rust_project_json(path: &Path) -> Option<PathBuf> {